html, body {
    margin: 0;
    height: 100%;
}

body {
    background: black;
    display: flex;
    flex-flow: column;
}

body > div {
    flex: 1;
    display: flex;
}

#header, #content, #navigation, #sidebar, #footer {
    background: grey;
    display: flex;
    border-radius: 10px;
    margin: 5px;
    padding: 5px;
}

#header, #footer {
    justify-content: center;
    flex-flow: column;
    text-align: center;
}

#header {
    height: 10%;
}

#content {
    flex: 1;
    overflow-y: scroll;
}

#navigation {
    order: -1;
    width: 10%;
}

#sidebar {
    width: 10%;
}

#footer {
    height: 5%;
}